So I had what I thought was worn down front brakes - a high pitched whine / squeal when braking. I had just replaced my rears (which were in poor, poor shape thanks to a cross-country drive). Bought new pads, but when I went to go swap them in, I realized the Mintex Red Boxes in there were barely worn down. I went ahead and replaced them anyway, and the squeal appears to have gotten a little quieter, but is still present. I can't tell if it's the fronts or the backs.

Anyone have any idea what could be causing this? To repeat, fresh pads on both the front and the back.